The present invention relates to a membrane capable of separation and purification of hydrogen from a mixed gas containing hydrogen, and of dissociation of hydrogen in a state of atoms. Further, the present invention relates to a method of preparation of a material used for the membrane. The present invention also relates to a method of treatment to activate the membrane.
At present, as a material for a gas hydrogen-separating membrane, Pd or Pd alloy is used, but their prices are so expensive as to be a major impediment to practical applications.
Therefore, a search for a metal membrane material of non-noble metal has been energetically made. In many instances, however, it has been necessary to coat a surface of the metal membrane with a noble metal, such as Pd and the like, in order to prevent the membrane surface from being oxidized, and to dissociate hydrogen molecules, which are then dissolved in the metal.
A number of electrochemical studies on hydrogen permeation have been reported, in which hydrogen is supplied in the form of ions, and a strong driving force for hydrogen permeation can be administered by applying voltage without applying mechanical force to the membrane. Accordingly, it is not assured that the membrane is utilizable for separation of gaseous hydrogen, which requires dissociation of hydrogen molecules, and uses pressure difference as a driving force, with the membrane left as it is.
With respect to amorphous (noncrystalline) Zrxe2x80x94Ni alloy, there is only an example in which a thin membrane of two layers of Pd and amorphous Zrxe2x80x94Ni alloy was formed on a silicon substrate by a sputtering method, and its rate of hydrogen permeation was electrochemically measured (J. O. Strxc3x6m-Olsen, Y. Zhao, D. H. Ryan, Y. Huai, R. W. Cochrane; xe2x80x9cHydrogen diffusion in amorphous Nixe2x80x94Zrxe2x80x9d; J. Less-Common Metals, Vol. 172-174 (1991) pp. 922-927). It has not been clearly understood whether or not amorphous Zrxe2x80x94Ni alloy can be applied directly to the separation and purification of hydrogen gas.
An object of the present invention is to provide a metal membrane for separation and dissociation of hydrogen, which has high permeability only with regard to hydrogen, sufficient mechanical strength and structural stability in an atmosphere of hydrogen, and which does not require, substantially, noble metals, such as Pd and the like.
Other and further objects, features, and advantages of the invention will appear more fully from the following description, taken in connection with the accompanying drawings.